1. Field of the Invention
The present invention relates to a diesel engine. In more detail, the present invention relates to a structural art of a combustion chamber of a diesel engine having a group injection hole nozzle.
2. Background Art
A combustion chamber of a diesel engine is demarcated by a top surface of a piston moving upward or downward and a wall surface of a cylinder liner. A fuel injection nozzle is provided in the upper portion of the combustion chamber. The fuel injection nozzle has a nozzle body forming an injection hole and a nozzle for opening and closing the injection hole. There is well known a group injection hole nozzle as a fuel injection nozzle with two or more injection holes adjacent to each other in series along the nozzle axis direction.
Compared with a single injection hole nozzle (normal nozzle), the group injection hole nozzle can be designed so as to have smaller diameter of the injection hole. Namely, compared with the normal nozzle, the group injection hole nozzle has smaller spray particle diameter, wider compound spraying angle, and larger spray tip range. Accordingly, by using the group injection hole nozzle, the performance of a mixture of air and fuel is improved so as to reduce combustion noise and smoke.
Generally, with regard to the normal nozzle, pass-through ability of spray is reduced in a diesel engine with a large bore diameter. However, with regard to the group injection hole nozzle, pass-through ability of spray is maintained in a diesel engine with a large bore diameter by interaction of adjacent sprays.
The Japanese Patent Laid Open Gazette 2006-070802 discloses a group injection hole nozzle comprising two injection holes provided in series and twisted against each other.
However, with regard to the group injection hole nozzle disclosed in the Japanese Patent Laid Open Gazette 2006-070802, when fuel injection is performed at downward movement process of a piston, fuel injected from the group injection hole touches the piston top surface and then moves to a wall surface of a cylinder liner and collides with the wall surface. Then, it is disadvantageous that burning of lubricating oil and dilution of lubricating oil occurs on the wall surface of the cylinder liner. It is also disadvantageous that localized insufficiency of air occurs in a combustion chamber so as to generate smoke.